Enthalpy and temperature of the phase change solid-liquid -An analysis of data of the elements using information on their structure

摘要

Latent heat storage with materials undergoing a phase change solid-liquid is gaining increasing interest due to its potential for applications in energy systems. The demand for optimized storage materials has led to an intensification of materials research in recent years. The research focuses mainly on developing materials with high storage density, and related to this the question what the theoretical limit is. For both it is necessary to understand what affects the melting enthalpy and melting temperature on the atomic and molecular level. For some material classes, especially metals, empiric rules or microscopic models have been developed that allow a qualitative and sometimes a rough quantitative prediction of the melting enthalpy and melting temperature. However, none of them is applicable to a wide variety of material classes or gives a general insight in the parameters affecting the melting enthalpy and melting temperature. In this paper, data of the elements with atomic number 1-95, and therefore very different material classes, are analyzed. In contrast to previous investigations, the focus is on relations between melting enthalpy and melting entropy, because these values relate to the microscopic structure. The results of the analysis show that several clusters exist among the elements. The differences between these clusters in the melting enthalpy as well as in the melting entropy can largely be explained by the microscopic structure of their member elements.